Helmets must be worn for a variety of reasons, under a variety of conditions. For example, helmets are utilized to contain respiration gases when it is desired to separate a worker from the environment. Such separation may be desired in manufacturing clean rooms and surgical operating rooms which should be protected from contamination by a worker's respiration, and in locations with an unpleasant or hazardous atmosphere from which the worker's respiration should be protected, as in the presence of toxic fumes or when firefighting. Safety helmets providing some impact protection are required in many jobs where a significant risk is perceived of objects striking a worker's head, including numerous construction, industrial, mining and firefighting jobs. Helmets providing even more impact protection than typical safety helmets are used in activities involving a significant risk of severe impact to the head, such as vehicle racing.
Wearing a helmet, particularly in a hot environment, is likely to make the worker's head even hotter, adding to the wearer's discomfort and fatigue, which will eventually impair performance. Driving some race cars has been likened to going to the office in an oven. Mines, construction and industrial sites are sometimes very hot, as are firefighting sites. The eventual degradation of performance from discomfort and fatigue adds to the dangers of injury. Accordingly, it is desirable to provide helmets which reduce discomfort to the wearer, thus enhancing comfort, reducing fatigue, and indirectly improving safety.
Various efforts have been made to deal with excessive heat around a helmet wearer's head For example, a helmet-mounted air conditioning system is described in U.S. Pat. No. 5,193,347 to Apisdorf. That apparatus includes a thermoelectric module (TEM), mounted in a housing on top of the helmet, which supplies cooled air to the area of the wearer's face. The extemally-mounted air conditioner of this invention may interfere with objects near the wearer's head, or cause the helmet to balance somewhat awkwardly.
In hot racing cars, mines, or industrial environments, it may be advantageous to provide conditioned breathing gas to a helmet wearer. Conditioning might be primarily cooling the air, or filtering out particulates, or modifying the gas mixture by removing or adding water or special gases, or some combination of the foregoing. Headgear air-flow control systems are known which filter the incoming air. For example, U.S. Pat. No. 5,035,239 to Edwards describes a "powered respirator" including a helmet having an electric fan located at the rear inside of the helmet. The fan impels air into the helmet, through a bag filter and thence to the wearer's facial area. This design has been described as probably not complying with impact resistance safety standards due to the fan presence inside the helmet. A passive gas exit is provided near the wearer's mouth, and the air is not particularly circulated to cool the wearer's head.
U.S. Pat. No. 5,113,853 to Dickey describes another helmet with a filtered air supply. Like that described in U.S. Pat. No. 5,035,239, this helmet employs an electric fan to pull in external ambient air through a filter. The filtered air is impelled across the wearer's head and thereafter is guided toward the wearer's facial area for the wearer to breathe. This device positions an intake fan near the crown of the wearer's head, within a large aperture through the shell of the helmet located near the crown of the wearer's head opening, and has a cap covering the fan but well separated from the shell. This helmet is not believed to meet rigorous impact safety standards. Further, it obligates the wearer to breathe air only after traveling over wearer's head and possibly through the wearer's hair. Since in a hot environment the wearer's head is likely to be sweaty, the flow of air doubtless has a cooling effect, but the quality of the air provided for respiration is degraded by that action. Furthermore, the helmet shell taught by Dickey is not monolithic, but includes a separate piece covering the fan which provides sharply angled lips significantly away from the helmet's smooth surface. Such a cover is believed to create a significant risk of interference with nearby objects when the head is moved. Interference may impede a wearer's quick reaction or movements, particularly in close quarters, thus impairing safety. Such interference risk is thus contrary to a primary motivator for the present invention, which is to enhance wearer safety.
Thus, a need exists for a helmet which provides cooling air circulation around the wearer's head by drawing air across the wearer's head without obligating the wearer to breathe the air thus previously used for evaporating sweat, and particularly for such a helmet which also meets stringent impact-protection standards. Desirably, such a helmet would not have unnecessary protrusions to catch on objects near the wearer's head, and would be light and well-balanced, and thus would interfere minimally with the wearer's head movements. Ideally, such a helmet would also provide means for providing conditioned air to the wearer, where the conditioning might entail cooling, cleaning, or varying the gas mixture such as by adding or removing H.sub.2 O, CO.sub.2, O.sub.2 or other gases.
Accordingly, it is an object of the present invention to provide a helmet which cools the head by drawing gas across a wearer's head and then exhausting it outside the helmet It is a further object of the present invention to provide such a helmet which further meets stringent impact protection standards. It is a further object to provide a helmet as described, further having means to provide conditioned gas to the wearer. It is a further object to provide a helmet which interferes as little as possible with a wearer's head movements.